Point sensor mounting apparatus

Abstract

A non-elastomeric sensor holding fixture using metal-to-sensor contact friction in a wheel slip control system maintains a wheel speed sensor in intimate contact with an exciter wheel without the excessive sensor wear which otherwise happens when the wheel speed sensor is held in place with resilient elastomeric holder. The use of metal-to-sensor frictional contact in the holding fixture avoids the hardening and seizing normally occurring in elastomeric-to-sensor frictional contact due to time and allows readjustment of sensor position after extended use.

What is claimed is: 
     
       1. In a wheel slip control system for automotive vehicles having a tone wheel, wheel speed sensor, wheel slip logic circuit and brake-relief solenoid valve, the improvement comprising: a holding fixture body containing a cavity therethrough;   support means for retaining said holding fixture body in a fixed position adjacent to a rotatable tone wheel within the hub of an automotive wheel;   a wheel speed sensor within the cavity in said holding fixture body;   a resilient metallic pressure means attached to said holding fixture body for applying force on the surface of and substantially normal to the axis of said generally cylindrical wheel speed sensor; and   wherein the cavity in said holding fixture body is generally an inverted U-shape with the legs of the U tapering inward from the vertical by a predetermined angle.   
     
     
       2. The system of claim 1 wherein said metallic pressure means is a flat spring. 
     
     
       3. The system of claim 2 wherein: the metallic pressure means urges the sensor into contact with the body at a plurality of body/sensor interface points.   
     
     
       4. The system of claim 3 wherein: a frictional resistance to sensor motion in the cavity results from contact between the metallic pressure means and the sensor and between the body and the sensor in accordance with the formula: R f  = F s  μ 1  /sin φ + F s  μ 2   Where:     R f  = frictional resistance to sensor motion;   μ 1  = static coefficient of friction between the sensor and the holding fixture;   μ 2  = static coefficient of friction between the sensor and the metallic pressure means;   F s  = force applied by the metallic pressure means on the sensor; and   φ = the predetermined angle of taper of the legs of the U-shaped cavity.   
     
     
       5. A sensor mounting apparatus comprising: a holding fixture body containing a cavity therein, the cavity having a first geometric cross-section;   a wheel speed sensor mounting in the cavity, the sensor having a second geometric cross-section different from the first cross-section;   resilient means mounted with the holding fixture body for urging the sensor into contact with the body at a plurality of body/sensor interface points; and   the cavity in the holding fixture body is generally an inverted U-shape with the legs of the U tapering inward from the vertical by a predetermined angle.   
     
     
       6. The mounting apparatus of claim 5 wherein: the resilient means urges the sensor into contact with the body with a normal force in accordance with the formula: F n  = F s  /2 sin φ where:     F n  = the normal force acting at the body/sensor interface points;   F s  = the force applied by the resilient means on the sensor; and   φ = the predetermined angle of taper of the legs of the U-shaped cavity.   
     
     
       7. The mounting apparatus of claim 6 wherein: a frictional resistance to sensor motion in the cavity results from contact between the resilient means and the sensor and between the body and the sensor in accordance with the formula: R f  = F s  u 1  /sin φ + F s  u 2   where:     R f  = frictional resistance to sensor motion;   u 1  = static coefficient of friction between the sensor and the holding fixture;   u 2  = static coefficient of friction between the sensor and the resilient means;   F s  = force applied by the resilient means on the sensor; and   φ = the predetermined angle of taper of the legs of the U-shaped cavity.   
     
     
       8. A sensor mounting apparatus comprising: a holding fixture body containing a cavity therein, the cavity having a U-shaped cross-section;   a wheel speed sensor mounted in the cavity, the sensor having a circular cross-section; and   resilient means cooperatingly mounted with the holding fixture for urging the sensor into contact with the body at a plurality of body/sensor interface points.   
     
     
       9. A sensor mounting apparatus comprising: a holding fixture body containing a cavity therein, the cavity having a U-shaped partial inner peripheral surface;   a sensor having cylindrical outer peripheral surface; and   resilient means cooperatingly mounted with the holding fixture for urging the sensor into partial peripheral interfacing contact between the sensor peripheral surface and the cavity inner peripheral surface.   
     
     
       10. A sensor mounting apparatus comprising: a holding fixture body containing a cavity therein, the cavity having U-shaped partial inner peripheral surface; and   resilient means cooperatingly mounted with the holding fixture at the opening of the U for providing an additional partial inner peripheral surface with the partial inner peripheral surface of the cavity.